Report build features in garage --help

src/model/Cargo.toml

@@ -26,6 +26,7 @@ blake2 = "0.9"
 err-derive = "0.3"
 git-version = "0.3.4"
 hex = "0.4"
+lazy_static = "1.4"
 base64 = "0.13"
 tracing = "0.1.30"
 rand = "0.8"

src/model/version.rs

@@ -1,3 +1,11 @@
+use std::sync::Arc;
+
+use arc_swap::ArcSwapOption;
+
+lazy_static::lazy_static! {
+	static ref FEATURES: ArcSwapOption<&'static [&'static str]> = ArcSwapOption::new(None);
+}
+
 pub fn garage_version() -> &'static str {
 	option_env!("GIT_VERSION").unwrap_or(git_version::git_version!(
 		prefix = "git:",
@@ -5,3 +13,11 @@ pub fn garage_version() -> &'static str {
 		fallback = "unknown"
 	))
 }
+
+pub fn garage_features() -> Option<&'static [&'static str]> {
+	FEATURES.load().as_ref().map(|f| &f[..])
+}
+
+pub fn init_features(features: &'static [&'static str]) {
+	FEATURES.store(Some(Arc::new(features)));
+}